The Science Behind the ‘Firenadoes’ of San Diego County

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In addition to the inherent tragedy of natural disasters there is almost always some pretty fascinating science behind them as well. Fire whirls – or ‘firenadoes’ as they’ve been coined on social media – are no exception. Footage of fire whirls forming in the wildfires currently raging through San Diego county have grabbed our interest over the past 24 hours, but what exactly is happening to create this amazing phenomenon?

Below is video from Fox 5 San Diego, including clips of the most recent fire whirls from yesterday.

Fire whirls occur when some sort of impediment, be it a grove of trees or a hillside, forces turbulent air to suddenly change direction. This process can form a whirlwind which, when rapidly heated by the fire below, can be shot into a vertical position and actually suck the flames skyward. The result is a tornado-like structure that can hurl embers and flaming debris great distances, compounding the impact of a given wild fire.

Often times the worst of a fire whirl is over after a few seconds since the heat quickly ventilates out of the vortex. Other times, gases surrounding the whirl can squeeze the spire into a tighter and tighter column, allowing the air inside it to behave as a solid, according to a study in the Journal of Combustion. Fire whirls are not just more astounding than your run of the mill wild fire section, they are also more destructive. Scientists estimate that fire whirls burn fuel – grass, trees, homes – three to seven times quicker than an open flame.